Sampled Grating Formation Using Universal Mold and Mask
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Solution Overview
Problem
The nano-imprint technique for forming sampled gratings in laser diodes is costly and time-consuming due to the need for multiple high-precision molds with different patterns, leading to high production costs and long fabrication times for varied structures.
Innovation Solution
A method involving a mold with periodic projections and recesses, a mask with alternating light obstructing and transmitting portions, and a photoresist layer exposure and etching process to control diffraction grating lengths, allowing for the formation of sampled gratings with various structures using a single type of mold, reducing production costs by using fewer and less expensive masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple high-precision molds with different patterns are used to form sampled gratings with various structures, then manufacturing precision is improved, but device complexity and production cost increase
Solution Approach 1:
A single mold with periodic projections and recesses is designed to serve multiple functions by combining it with different masks. The mask varies the light transmission pattern during exposure, allowing one mold to produce multiple sampled grating structures with different diffraction grating lengths and configurations, eliminating the need for multiple specialized molds
Solution Approach 2:
A mask is introduced as an intermediary element between the light source and the photoresist layer. This mask controls which portions of the photoresist are exposed to light during the nano-imprint process, enabling the formation of different sampled grating structures using the same mold and photoresist pattern, thereby reducing mold complexity
2Manufacturing precision
If multiple high-precision molds with different patterns are prepared, then manufacturing precision is improved, but production cost increases
Solution Approach 1:
The mold is designed as a universal tool that can produce multiple sampled grating variants. By fixing the mold pattern and varying only the mask configuration during exposure, the same expensive mold can manufacture different laser diode products, significantly reducing the need for multiple high-cost molds and their associated fabrication expenses
Solution Approach 2:
The mask is designed as a simpler, less expensive component compared to the high-precision mold. By placing the variability function in the mask rather than the mold, the system replaces expensive reusable molds with cheaper masks that can be easily manufactured and replaced if needed, reducing overall production cost
3Manufacturing precision
If multiple high-precision molds with different patterns are used, then manufacturing precision is improved, but fabrication time increases
Solution Approach 1:
The mold serves as a universal pattern source that remains constant throughout production. Different sampled grating structures are achieved by changing the mask configuration during the exposure step, eliminating the time-consuming process of switching between multiple specialized molds and their associated alignment and setup procedures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the production of sampled gratings with diverse structures at a low cost, suppressing deviations in diffraction grating periods and recess numbers, thereby enhancing the efficiency and cost-effectiveness of laser diode manufacturing.
Implementation Method 1
a mold including a pattern having periodic projections and recesses in correspondence with the shape of the diffraction grating is pushed against the resin layer, and the resin layer is hardened in this state. This causes the pattern having projections and recesses of the mold to be transferred to the resin layer.
Implementation Method 2
exposing a portion of the photoresist layer by irradiating the photoresist layer with exposing light through the mask and the patterned resin portion; forming a patterned photoresist layer by developing the photoresist layer
Implementation Method 3
etching the substrate using the patterned photoresist layer to form a first portion without a pattern having projections and recesses and second portion with a pattern having projections and recesses
Data Source
AI summary
A method of forming a sampled grating includes the steps of preparing a substrate; preparing a nano-imprinting mold including a pattern surface on which projections and recesses are periodically formed; preparing a mask including a light obstructing portion and a light transmitting portion that are alternately provided; forming a photoresist layer and a resin portion in that order on the substrate; forming a patterned resin portion having projections and recesses by pressing the pattern surface of the mold into contact with the resin portion and hardening the resin portion while maintaining the contact; exposing a portion of the photoresist layer by irradiating the photoresist layer with exposing light through the mask and the patterned resin portion; forming a patterned photoresist layer by developing the photoresist layer; and etching the substrate using the patterned photoresist layer.